Data transmission of downhole recorded measurements by untethered object to a toolstring inside a well

ABSTRACT

An untethered sensing object able to sense and record well fluid and wellbore parameters. The untethered sensing object is adapted to transmit recorded data towards a communication module of a toolstring, whereas the toolstring is conveyed from surface and reaches a proximity distance with the untethered sensing object inside the well fluid of a wellbore. The untethered sensing object includes at least one sensor, an acquisition module, a recording module and a transmitting module.

BACKGROUND

This disclosure relates generally to methods and apparatus for providinga measurement inside a wellbore containing well fluid. This disclosurerelates more particularly to methods and apparatus for transmitting datarecorded by an untethered sensing object inside the well fluid of thewellbore towards a toolstring conveyed from surface and reaching aproximity distance with the untethered sensing object.

The first nine figures (FIGS. 1 to 9) refer to one environment examplein which the methods and apparatus for providing a plug with anuntethered object inside a tubing string containing well fluid describedherein may be implemented and used.

FIG. 1 illustrates a typical cross section of an underground sectiondedicated to a cased-hole operation. The type of operation is oftendesignated as Multi-Stage-Stimulation, as similar operations arerepeatedly performed inside a tubing string in order to stimulate thewellbore area.

The wellbore may have a cased section, represented with tubing string 8.The tubing string contains typically several sections from the surface12 until the well end. The tubing string represented schematicallyincludes a vertical and horizontal section. The entire tubing stringcontains a well fluid 7, which can be pumped from surface, such aswater, gel, brine, acid, and also coming from downhole formation such asproduced fluids, like water and hydrocarbons.

The tubing string 8 can be partially or fully cemented, referred to ascemented stimulation, or partially or fully free within the borehole,referred to as open-hole stimulation. Typically, an open-holestimulation will include temporary or permanent section isolationbetween the formation and the inside of the tubing string.

The bottom section of FIG. 1 illustrates several stimulation stagesstarting from well end. In this particular well embodiment, at leaststages 14 a, 14 b, 14 c have been stimulated and isolated from eachother. The stimulation is represented with fluid penetration inside theformation through fracturing channels 13, which are initiated from afluid entry point inside the tubing string. This fluid entry point cantypically come from perforations or sliding sleeves openings.

Each isolation includes a plugging element 6 with its untethered object1, represented as a spherical ball as one example.

The stimulation and isolation are typically sequential from the wellend. At the end of stage 14 c, after its stimulation 13, anotherisolation and stimulation may be performed in the tubing string 8.

FIG. 2 depicts a sequential step of FIG. 1 with the preparation ofsubsequent stage 14 d. In this representation, a toolstring 10 isconveyed via a cable or wireline 15, which is controlled by a surfaceunit 16. Other conveyance methods may include tubing conveyedtoolstring, coiled tubing. Along with a cable, a combination of gravity,tractoring and pump-down may be used to bring the toolstring 10 to thedesired position inside the tubing string 8. In FIG. 2, the toolstring10 conveys an unset plug 17, dedicated to isolating stage 14 c fromstage 14 d.

FIG. 3 depicts a close-up view of FIG. 2, focused on toolstring 10 andunset plug 17.

FIG. 4 depicts a sequential view of FIG. 3, whereby the toolstring 10 isactuated to set the plugging element 6 inside the tubing string 8,typically uphole of the last entry points for fracturing channels 13.

FIG. 5 depicts a sequential view of FIG. 4, whereby the toolstring 10 ispulled away of the set plugging element 6. The toolstring 10 wouldtypically perform perforations uphole of the set plugging element 6.

FIG. 6 depicts a sequential view of FIG. 2 or of FIG. 5, whereby furtherperforating inside the tubing string 8 has been performed uphole of theset plugging element 6. Typically, the set plugging element 6 creates arestriction in the tubing string 8 able to receive, at a later time, anuntethered object such as a ball. The toolstring 10 and cable 15 of FIG.2 or of FIG. 5 have then been removed from the tubing string.

FIG. 7 depicts a sequential view of FIG. 6, where an untethered object 1is pumped from surface 12 with the well fluid 7 inside the tubing string1.

FIG. 8 depicts a sequential view of FIG. 7, where the untethered object1 lands on the set plugging element 6 and creates a well fluid isolationbetween the uphole and downhole sides of the plug position.

FIG. 9 depicts a sequential view of FIG. 8, where further pumping fluid18 may increase pressure uphole of the position of the set pluggingelement 6, including on the untethered object 1, of stage 14 d.Additional pumping rate and pressure may create a fluid stimulation 13inside the formation located on or near stage 14 d. When the stimulationis completed, another plug may be set and the overall sequence of stages1 to 5 may start again. Typically, the number of stages may be between10 and 100, depending on the technique used, the length of well andspacing of each stage.

There is a continuing need in the art for methods and apparatus forproviding an untethered object on the plug inside a tubing stringcontaining well fluid. Preferably, the untethered object includes asensing and measuring module and acts as an isolation device underpressure differential.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more detailed description of the embodiments of the disclosure,reference will now be made to the accompanying drawings.

FIG. 1 is a wellbore cross-section view of typicalMulti-Stage-Stimulation operation ongoing, with three stages completed.

FIG. 2 is a wellbore cross-section view of toolstring conveyance toinstall the third isolation device for the fourth stage.

FIG. 3 is a Close-up cross-section view of FIG. 2.

FIG. 4 is a Close-up cross-section view of toolstring installing 3rdisolation device.

FIG. 5 is a Close-up cross-section view of 3rd isolation deviceinstalled and toolstring moved up.

FIG. 6 is a wellbore cross-section view of the third stage isolationdevice being set and the fourth stage being perforated.

FIG. 7 is a wellbore cross-section view of an untethered object beingdropped inside the well and moving towards the third isolation devicethrough the perforated area.

FIG. 8 Wellbore cross-section view of 3rd stage with untethered objectbeing landed on isolation device.

FIG. 9 is a wellbore cross-section view of the fourth stage isolatedfrom the third stage by a plug and untethered object, and completed withpressure pumping operation.

FIG. 10 is a cross-section view of an untethered sensing object.

FIG. 11 is a cross-section view of the untethered sensing objectpositioned across a plugging element.

FIG. 12 is an enlarged view of FIG. 11, depicting the untethered sensingobject positioned across the plugging element, during the stimulationoperation.

FIG. 13 is an isometric cross-sectional view of the untethered sensingobject.

FIG. 14 is an external isometric view of the untethered sensing object.

FIG. 15 is a schematic isometric wireframe view of another untetheredsensing object with a tetrahydric sensing device disposition.

FIG. 16 is another view, from the top, of the schematic isometricwireframe of the other sensing untethered object with a tetrahydricsensing device disposition.

FIG. 17 is another view, from the front, of the schematic isometricwireframe of the other sensing untethered object with a tetrahydricsensing device disposition.

FIG. 18 is a cross-section view of the untethered sensing object of FIG.15, positioned across a plugging element

FIG. 19 depicts four recording graphs of pressure over time, recorded bythe four sensing devices on the untethered sensing object of FIG. 18.

FIG. 20 is a cross-section view of another embodiment with toolstringincluding three untethered sensing carried objects.

FIG. 21 is a close-up isometric view of a plugging element including acup, the left view without and the right view with the three untetheredsensing carried objects.

FIG. 22 is an isometric view the three untethered sensing carriedobjects seating on the cup. The plugging element and tubing string aredepicted in wireframe for position reference.

FIG. 23 is a wellbore cross-section of toolstring conveyance to installthe 4^(th) isolation device, sequential to FIG. 9, with the toolstringincluding a communication device.

FIG. 24 is a close-up cross-section view of FIG. 23 with the toolstringincluding a communication device

FIG. 25 is a close-up cross-section view of wellbore section withtoolstring communicating with the untethered sensing object.

FIG. 26 is a cross-section view of wellbore section with toolstringcommunicating with the untethered sensing object and setting a pluggingelement.

FIG. 27 is a cross-section view of wellbore section with toolstring withcommunication device pulled away from set plugging element.

FIG. 28 is a wellbore cross-section with toolstring with communicationdevice being retrieved back to surface.

FIG. 29 is a close-up cross-section view of the untethered sensingobject having its external shell dissolving.

FIG. 30 is a wellbore cross-section view of two untethered sensingobjects having their external shell dissolved, and free to move insidethe tubing string.

FIG. 31 is a wellbore cross-section view with four untethered sensingobjects having their external shell dissolved, and moving upwards insidethe tubing string.

FIG. 32 is a wellbore cross-section view with four untethered sensingobjects having their external shell dissolved, and flowing back tosurface.

FIG. 33 is a close-up cross-section view of FIG. 32, showing anuntethered sensing object having its external shell dissolved andretrieved at surface.

FIG. 34 is a wellbore cross-section view, sequential of FIG. 32, wherebythe tubing string is free of all untethered sensing objects, after beingretrieved or dissolved.

FIG. 35 is a wellbore cross-section view, sequential of FIG. 34, wherebythe tubing string is free of all plugging elements, after beingretrieved or dissolved.

FIG. 36 is an isometric cross-section view of another embodiment ofuntethered sensing object, as a pill shape, with two sensing devicesplaced on the long diameter.

FIG. 37 is a cross-section view of the pill untethered sensing object,with two sensing devices placed on the long diameter.

FIG. 38 is an external isometric view of the pill untethered sensingobject, with two sensing devices placed on the long diameter.

FIG. 39 is a wellbore cross-section view with the pill untetheredsensing object seating on a plugging element.

FIG. 40 is close-up cross-section view of FIG. 39 with the pilluntethered sensing object seating on a plugging element.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the following disclosure describes severalexemplary embodiments for implementing different features, structures,or functions of the invention. Exemplary embodiments of components,arrangements, and configurations are described below to simplify thedisclosure; however, these exemplary embodiments are provided merely asexamples and are not intended to limit the scope of the invention.

FIG. 10 represents a possible embodiment of a sensing untethered object1.

FIG. 10 represents a cut view of the sensing untethered object 1. Theuntethered sensing object 1 is represented as an overall sphere shape,though it may have the shape of a pill, of a dart, of a bullet, or apoly-facet volume.

The two main functions, among others, of the untethered sensing object 1would be to perform sensing operation and withstand fluid pressure bothhydrostatically and as a tubing string fluid barrier. Components andfeatures included inside the untethered sensing object 1 would thereforecope towards those two main functions. Additional functions describedspecifically after FIG. 21 would include communication capacity.

A well fluid 7 may be present surrounding the untethered sensing object1, as for example a pump down fluid, a frac fluid, an injection fluid.The well fluid 7 may be produced by the well itself, as a flow back orproduction fluid. The well fluid 7 may include a mixture of gases,fluids, condensates, like possibly water or hydrocarbon-based fluids orvapors.

The untethered sensing object 1 may include some dissolvable materials.Dissolvable materials typically include dissolvable metals, likemagnesium alloys, aluminum alloys, iron alloys, dissolvable composites,including metal matrix composites, dissolvable plastics, like PLA,dissolvable elastomers. All or a portion of the further describedcomponents included in the untethered sensing object 1 may includedissolvable materials.

The untethered sensing object 1 may contain an external shell 2,represented in two matching shell sections 2 a and 2 b. The two matchingshell sections 2 a and 2 b are represented as half spheres as an exampleof manufacturing and assembly. The external shell shape 2 containspreferably continuous surface such as spherical, conical, cylindrical,frusto-conical or combination thereof. In other embodiment, the externalshell 2 may contain facets or polygonal faces.

The external shell sections 2 a and 2 b may be assembled together toform a tight connection between the two or more sections. Suchconnection can occur through a threaded connection, a welded connection,a press fit connection, a friction connection or combination thereof.

The external shell 2 could be designed, in particular through itsthickness and material choice, to withstand an hydrostatic pressure ofwell fluid 7, ranging typically between 100 and 20,000 psi, as well asto withstand a pressure differential of well fluid 7 across the wholeuntethered sensing object 1, ranging typically also between 100 psi and20,000 psi, both pressures being potentially cumulative.

The pressure tightness between the external shell sections 2 a and 2 bmay be improved by adding one or more sealing features such as an O-ringor gasket at the contact area 25 between both external shell sections 2a and 2 b.

Possibly, other embodiment may allow the penetration of well fluid 7inside the untethered object through the external shell sections 2 a and2 b, and therefore include a fluid barrier at another level such as aninternal shell, or by allowing the internal components to sustain thehydraulic pressure when using for example pressure compensatedcomponents.

A sensing carrier 19 could be placed inside the external shell section2. The sensing carrier 19 could be a frame, represented here mainlyspherical, fitting inside the external shell sections 2 a and 2 b, andcould contain multiple parts assembled together. The primary function ofthe sensing carrier 19 would be to hold the sensing devices 4 in place,represented as 4 a, 4 b and 4 c. In this configuration, the untetheredsensing object 1 would include three sensing devices, 4 a, 4 b and 4 c,though any number of sensing devices from 1 to 100 would be possible.The sensing devices 4 a, 4 b, 4 c would typically be held in place bythe sensing carrier 19 for position stability. The assembly of thesensing devices 4 a, 4 b, 4 c within the sensing carrier 19 wouldinclude for example welding, press fitting, screwing, over-molding,pinning. The sensing devices are typically independent sensors whichacquire data from measuring physical characteristics of the well fluidor of objects in contact or close distance. Measured data includetypically pressure, temperature, sound reflection, resonance, magnetism,and fluid characteristics such as salinity, pH, chemical composition,viscosity, resistivity. Sensors could also include depth, positioningmeasurement, locating the untethered sensing object 1 relative to thetubing string 8, by measuring CCL, known as Casing Collar Locator ornatural formation radioactivity such as gamma-ray.

Sensing devices 4 can sense at low frequency from seconds to days permeasurement, as well as sense at high or very high frequency up to10,000 Hz. A high frequency measurement would typically be relevant forpressure, resistivity or sonic responses.

Fluid sampling could also be performed by the sensing devices 4.

Each sensing device 4 could be different, or could be similar. Eachsensing device 4 could measure one parameter as well as multipleparameters.

The untethered sensing device 1 may include an electronic module 5. Thiselectronic module could be placed inside a hollow volume of the sensingcarrier 19 and be held in place using fasteners such as screws, pins,springs or alternatively held permanently in place using welding,brazing, press-fitting. The electronic module 5 may typically includethree sections or functions: a power section, like a battery, anacquisition section to acquire the parameters measured by sensingdevices 4 a, 4 b, 4 c, and a memory section to keep the parametersmeasured and acquired in a digital memory form. In addition, a fourthfunction could be included, as a transmitter, for in-and-outcommunication, like receiving orders from an external device andtransmitting out data to an external device.

Wiring 21 may connect the electronic module 5 with the different sensingdevices 4 a, 4 b and 4 c. Note that different wiring options arepossible, such as linking the sensing devices 4 a, 4 b, 4 c togetherbefore reaching the electronic module 5. Additionally, a wirelesstransmission between those components could be possible, usingtechnologies like radio frequencies, optical, sonic, electromagneticinduction (RFID).

Sensor protectors 22 could be part of the external shell sections 2 aand 2 b, or could be separate parts matching the external surface of theshell section 2 a and 2 b. The size and position of the sensor protector22 could help the mounting of each sensing devices 4 a, 4 b and 4 c.Each sensor protector 22 could be mounted inside the shell sections 2 aand 2 b through typical permanent or temporary assembly, such ascrewing, press-fitting, gluing, over-molding, welding, brazing. Thesensor protector 22 could include an orifice channel 3 linking the wellfluid 7 with the sensing devices 4 a, 4 b and 4 c. This orifice channel3 would be necessary for certain type of measurement requiring thedirect contact of the well fluid 7 with the sensing device 4 a, 4 b or 4c, such as for a pressure measurement. This orifice channel 3 would incontrary not be necessary for other type of measurement such as sonic ormagnetic. In some application where the isolation tightness is importantbetween the untethered sensing device 1 and the plugging element 6, thediameter of the orifice channel 3 could be kept relatively smallcompared to the main dimensions of the untethered sensing devices. Withan untethered sensing device main external dimension in the order ofinches, from 0.5 to 10 inches for example, the orifice channel diametercould be several magnitudes smaller, typically from 0.001 to 0.1 inches.

The material of the sensor protector 22 could include all the materiallisted for the untethered sensing device 1, such as dissolvable ornon-dissolvable metals, plastics, composites, elastomers, plus materialsspecially dedicated to the sensing devices 4 a, 4 b and 4 c positionedat proximity, such as non-magnetic materials, non-conductive orlow-dielectric material like PEK or PEEK.

Sealing sections 20 with O-ring, gaskets may be added to ensure somepressure tight volumes inside the untethered sensing object 1, topotentially keep the electronics module 5 away from well fluid 7.Alternatively, the electronics module 5 could be safe pressure tight ifincluding a pressure resistant shell enclosure. Sealing sections 20could also ensure that the overall untethered sensing object 1 isself-sealing avoiding well fluid 7 passage through its own volume.

FIG. 11 represents a similar sensing untethered object 1, as describedin FIG. 10, seating on a plugging element 6, inside a tubing string 8,which contains well fluid 7.

The plugging element 6 may be a fracturing plug, a seat, a portion of asleeve, of a packer, of a liner hanger, of a pipe recess, or any entity,permanent or temporary which could provide a permanent or temporary stopfor the sensing untethered object 1, within the tubing string 8.

The minimum cross-sectional dimension 60 of the plugging element 6 maybe smaller than the cross-sectional dimension 61 of the untetheredsensing object 1. The untethered sensing object 1 would thereforeperform a permanent or temporary isolation of fluid or gas inside thetubing string 8, between uphole 23 and downhole 24 portion of theisolated tubing string 8, along an isolation contact line 30 betweenuntethered sensing object 1 and the plugging element 6.

The isolation contact line 30, shown on FIG. 11 as a dashed line,represents the contact line or area between the plugging element 6 andan untethered sensing object. With a typical cylindrical pluggingelement 6 and a typical spherical untethered object 1, the isolationcontact line would be circular or include an area band which would be aspherical zone. As represented in FIG. 11, with cross-sectionaldimension 60 and 61 being of similar magnitude, within 0.001 and 1 inch,while keeping the cross-sectional dimension 60 smaller than thecross-sectional dimension 61, the isolation contact line 30 wouldseparate a spherical untethered sensing object 1 in about twohemispheres of similar sizes.

The isolation performed by the sensing untethered object 1 and pluggingelement 6 within tubing string 8 could provide a pressure differentialhold uphole 23 compared to downhole 24 for the well fluid 7. A typicalpressure differential could be between 100 and 20,000 psi across boththe plugging element 6 and the untethered sensing object 1.

As represented on FIG. 11, the different sensing devices 4 a, 4 b and 4c, could be positioned uphole 23 and downhole 24 of the isolationcontact line 30. Therefore, the untethered sensing object 1 couldperform measurement both uphole 23 and downhole 24 of the isolationcontact line 30. An application example would be to evaluate a tight orleaking isolation, recording a differential pressure, a differentialtemperature or a differential fluid characteristic, on both sides of theisolation contact line 30.

The isolation performed by the sensing untethered object 1 on theplugging element 6 along the contact line 30 could be tight or loose. Aloose isolation would allow a leakage of well fluid 7 passing throughthe contact line 30, with flowrates ranging from 0.01 to 100 gallons perminute [0.038 to 379 liters to minute]. A tight isolation could reachgas type sealing, following a V0 or a V3 norm. The isolation may alsodepend on the well fluid 7, such as viscosity or solid content, likesand particles, viscosity enhancer, or fibers like PLA.

When considering some portions of the untethered sensing object 1 aswell as some portions of the plugging element 6 to be dissolvable, theisolation tightness along contact line 30 may evolve with time.Therefore, the isolation between the untethered sensing object 1 and theplugging element 6 may be temporary, from a few minutes to a few months,depending on the material characteristics of the untethered sensingobject 1 and the plugging elements 6. Further details about dissolvingfeatures are developed in FIG. 29 to FIG. 35.

FIG. 12 represents a cross-section of a well portion of a typicalmulti-stages stimulation described in FIG. 1 to FIG. 9. In FIG. 12, theuntethered sensing object 1 is seating on a plugging element 6 within atubing string 8 and could measure properties of well fluid 7, uphole, asvolume 23, and downhole, as volume 24, simultaneously during anintervention inside the wellbore 8. Represented are fracture penetrationand stimulation propagation 13, symbolizing hydraulic fracturing fluidentry.

FIG. 13 represents an isometric cut view of a similar untethered sensingobject 1 as in FIG. 11.

FIG. 14 represents volumetric isometric view of a similar untetheredsensing object 1 as in FIG. 11.

FIGS. 15, 16 and 17 represents different orientation views of anotherembodiment of an untethered sensing object 1. The represented embodimentof an untethered sensing object 1 includes four sensing devices 4 a, 4b, 4 c and 4 d. The four sensing devices are displayed at the fourvertex corners of a virtual regular tetrahedron, included inside aspherical shell 2. This particular configuration of four sensing deviceswould ensure that at least one sensing devices is positioned within oneof the two hemispheres included inside a sphere, independent from themiddle cutting plane position, cutting the sphere in two similarportions.

FIG. 18 represents a cut view of a tubing string 8, containing wellfluid 7, whereby an untethered sensing object 1, represented as anisometric view, as described in FIGS. 15, 16 and 17, would have landedonto a plugging element 6. With the particular tetrahedralconfiguration, at least one sensing device out of 4 a, 4 b, 4 c or 4 dwould be positioned towards volume 23, uphole of the isolation contactline 30, and at least one of the other sensing devices out of 4 a, 4 b,4 c or 4 d would be positioned towards volume 24, downhole of theisolation contact line 30. Overall, independent of the relative positionof the untethered sensing object to the plugging element 6, thetetrahedral configuration of four sensing devices would always allow tohave at least one measurement towards uphole and one measurement towardsdownhole of the isolation contact line 30. This would not always be trueif only three sensing devices 4 were positioned on a spherical externalsurface of the untethered sensing object 1.

FIG. 18, is an illustration of this geometrical configuration, and showsin this case two sensing devices 4 a and 4 b towards volume 23, upholeof isolation contact line 30, and two sensing devices 4 c and 4 dtowards volume 24, downhole of isolation contact line 30. Depending onthe landing position of the untethered sensing object 1 on the pluggingelement 6, other sensing configurations would be possible, like onesensing device towards volume 23, uphole of isolation contact line 30,and three sensing devices towards volume 24, downhole of 30, or threesensing devices towards volume 23, uphole of circular contact 30, andone sensing device towards volume 24, downhole of isolation contact line30.

FIG. 19 represents a possible pressure recording of the four sensingdevices 4 a, 4 b, 4 c, 4 d, on a spherical untethered object 1,configured as in FIG. 18.

Four graphs are represented. Graph 41 represents the pressure recordingover time of sensing device 4 a. Graph 42 represents the pressurerecording over time of sensing device 4 b. Graph 43 represents thepressure recording over time of sensing device 4 c. Graph 44 representsthe pressure recording over time of sensing device 4 d. For clarity,each graph contains the same x-axis time unit and scale represented herefor time 0:00 to 3:00, in the format hour for the first digit andminutes for two last ones, in other terms from time zero to three hours.The y-axis represents fluid pressure, measured in psi, pound per squareinches [1 psi=6895 Pa].

As recorded by sensing devices 4 a, 4 b, 4 c and 4 d, represented ingraphs 41, 42, 43, 44, the first thirty minutes, from time 0:00 to about0:30, would represent a pressure increase from 0 psi to 5,400 psi,represented as a pressure ramp, in curve section 31. The pressure rampcould represent a hydrostatic pressure increase due to an increase ofdepth of the sensing devices 4 a, 4 b, 4 c and 4 d as they travel fromthe ground surface to the landing position. For example, if a wellcontains 12,000 feet of vertical depth and if using a pressure gradientof 0.45 psi/ft, depending on well fluid density, the recorded pressurecould reach 5,400 psi. The time of thirty minutes hour could representthe time for the untethered sensing object 1 to reach its landingposition on the plugging element 6, while travelling through a verticalportion of a well. The travel of the untethered sensing object 1 couldoccur through gravity fall, pump down with well fluid 7 from surface orside injection points, or being pushed or carried within a toolstring10, conveyed from surface or through tractoring. The configurationdescribed whereby the untethered sensing object 1 is carried within thetoolstring 10 could refer to a so-called ball-in-place operation whereone or more untethered objects are carried within the toolstring 10which is also used to install the plugging element 6. Further example ofthis application can be seen in FIGS. 20, 21 and 22.

For graphs 41 and 42, the second portion of the pressure curve,represented in curve section 32, could represent a time period duringwhich the vertical position of the untethered sensing object 1 does notchange relative to ground 12, as referred for example in FIG. 8, and noadditional pressure from well fluid 7 is acting on the untetheredsensing object 1. It could be the case if the untethered object isfurther travelling horizontally, pumped, carried or pushed, or stopped afixed location inside the tubing string 8, as for example if landed on aplugging element 6. The time period of curve section 32 could last about40 minutes before recording a sharp increase of pressure and reach curvesection 33. The curve section 33 could represent the pressure increasedue to a pumping from surface or from entry points uphole of theuntethered sensing object 1. A typical increase of fluid pressure isdepicted in graph 41 and 42 for the curve section 33, and could reach8,000 psi additional compared to curve section 32, reaching a total of13,400 psi. The pressure increase of 8,000 psi could be referred asstimulation or fracturing pressure, which could be linked in amulti-stage stimulation operation with fluid 7 pumping. In thissituation example, the pressure increase could only be recorded by thesensing devices located uphole of the isolation contact line 30 of theuntethered object 1, as long as substantial isolation is achieved by theuntethered sensing object 1 with the plugging element 6. Substantialisolation would result in avoiding the pressure of the well fluid 7 toreach the downhole section of the tubing string 8, downhole of theisolation contact line 30, as depicted for example in FIG. 18 or in FIG.9. In this example, the duration of the pressure increase recorded bycurve section 33 is about one hour and a half, from time 1:10 to 2:40.Subsequently, on graphs 41 and 42, curve section 34 represent the returnto similar pressure as curve section 32, namely around 5,400 psi. Thispressure drop could happen subsequentially of stimulation or fracturingpressurizing ending.

For graphs 43 and 44, since having both sensing devices 4 c and 4 d,downhole of potential pressure increase, the pressure level would beflat, represented as curve section 35, staying at similar pressurelevels as curve section 32 and 24 of graphs 41 and 42, namely around5,400 psi.

The conjunction of these recorded graphs relative to the position of thesensing devices 4 a, 4 b, 4 c, and 4 d with respect to the isolationcontact line 30 would be a potential proof of the efficiency of theisolation realized by both the untethered sensing device 1 and theplugging element 6 within the tubing string 8. Note that sensing devices4 a, 4 b, 4 c and 4 d could also record the pressure response of wellfluid 7 passing outside of the tubing string 8, potentially bridgingfracturing channels 13, located uphole and downhole of the isolationcontact line 30.

In this example, graphs 41, 42, 43, 44 show a timeframe of about threehours from 0:00 to 3:00, though longer durations would be possible,typically from several hours to several months. An extended recordingtimeframe would be useful if the operations displayed by the sequentialcurve segments 31, 32, 33, 34 would last longer time, as directed bywell operation. In addition, extended recording timeframe could allow torecord data while subsequent stages are stimulated. This could be thecase in a multi-stage stimulation operation, like the one represented inFIG. 9, where multiple untethered sensing objects 1 could recordsimultaneously. In FIG. 9, this would mean that the untethered sensingobject 1 from stages 14 d, 14 c and 14 b are all recording data while apumping operation 18 is occurring from surface. Simultaneous recordingof well parameters would help understanding and analyzing the effect ofthe pressure pumping 18 on the current stage 14 d, but also onpreviously stimulated stages 14 c and 14 b. In particular, a multi-pointpressure or temperature data recording would help determining sideeffects of subsequent stage pumping, such as fluid channeling, bridging,communicating between the different fracturing channels 13 of multiplestages 14 d, 14 c and 14 b.

Further useful well operation parameters could be recorded by theuntethered sensing objects 1 during additional subsequent operations,like well flow back, re-pumping, well production.

Possible retrieval of data recorded by the untethered sensing objects 1would be further exposed in FIG. 23 to FIG. 36.

FIG. 19 displaying a pressure recording along four sensing points isonly one illustration of the potential usage of the untethered sensingdevice 1. Temperature, fluid characteristics, position over time, upholeand downhole of the isolation contact line 30, could also helpinterpreting the efficiency and the effectiveness of a pressurestimulation while isolating stages at the position of the untetheredsensing object 1.

Note also that for any recorded parameters by the sensing devices 4 a, 4b, 4 c, 4 d, for the different configurations depicted in FIG. 12 orFIG. 15, the recorded frequency could play an important role. Withrespect to FIG. 19, pressure graphs, the represented time scale could beseconds or minutes, though a high frequency recording, ranging from 10Hz to 10,000 Hz, could reveal other aspect of well operations. Keepingthe example of pressure sensing, recording pressure variations at a highfrequency could help identify localized pressure response in theformation with fluid penetrating fracture channels 13. Spectral analysiscould further be used to map pressure responses within the differentchannels 13 located within stimulation stages 14 a, 14 b, 14 c and 14 dif referring to an operation depicted in FIG. 9.

FIGS. 20 to 22 represent another embodiment of the untethered sensingobject.

FIG. 20 represents a possible ball-in-place operation. The pluggingelement 6 may include an additional plugging portion, a cup 51, whichcould represent a mandrel of the plugging element. The cup 51 would fitwithin the plugging element 6, having typically at least a contact zone52, to provide a fluid flow isolation across the assembly made of thecup 51 with the plugging element 6. The contact zone 52 could becompared to the isolation contact line 30, between the plugging element6 and the sensing untethered object 1, as described in FIG. 18. The cup51 could be part of the plugging element 6 and be carried together bythe toolstring 10. The cup 51 would therefore be installed during asimilar process of plugging element 6 setting described in FIGS. 3, 4and 5.

The cup 51 could include one or more orifices 53. The orifice 53 wouldinclude typically one or more sections with cylindrical, spherical,conical shapes or combination thereof. The orifice 53 would typicallyprovide a flow-through area in which well fluid 7 could flow freelyuphole or downhole.

The toolstring 10 could carry one or more sensing untethered carriedobject 50. In FIG. 20, three sensing untethered carried objects arerepresented as 50 a, 50 b, 50 c. The number of sensing untetheredcarried objects would typically match the number of orifices 53 includedinside the cut 51. Each sensing untethered carried object 50 a, 50 b or50 c could be very similar to the sensing untethered object described inFIG. 11. As for the shape matching between the sensing untethered object1 with the plugging element 6, each sensing untethered carried object 50a, 50 b or 50 c would have a shape matching between its outsidedimension and the inner dimension of each orifice 53. If taking theexample of a spherical outer shape for the sensing untethered carriedobject 50, the diameter of the sphere would typically be greater thanthe inner diameter of each orifice 53, assuming for example acylindrical orifice. The objective being the possibility of each sensinguntethered carried object to seat uphole on the orifice and provide awell fluid isolation from the uphole direction. Other shape matchingbetween the sensing untethered object 50 and the orifice 53 would bepossible, such as conical contact, spherical contact.

The number of sensing untethered carried object would typically bebetween one and ten. Typically, each sensing untethered carried objectwould have an equivalent number of orifices 53 on the cup 51.

The release of the sensing untethered carried objects 50 a, 50 b and 50c, would typically occur after the positioning and setting of theplugging element 6 with the cup 51 inside the tubing string 8. Thetoolstring 10 would therefore mechanically free-up the different sensinguntethered carried objects 50 a, 50 b, 50 c, through typically a pumpingaction of well fluid 7 from uphole towards downhole, like pumping fromsurface, or through an ejection mechanism within the toolstring 10, suchas a spring or a piston. The release travel of the sensing untetheredcarried objects 50 a, 50 b and 50 c is symbolized with the arrow 55,from the toolstring 10 towards the cup 51 linked with the pluggingelement 6, within the well fluid 7.

It is to be noted that the three untethered objects within thetoolstring are represented to be similar and as sensing untetheredcarried objects 50 a, 50 b, 50 c, though a combination of sensing andnon-sensing untethered object might be used. For example, one sensinguntethered carried object 50 a may perform one or more specificmeasurements, while another sensing untethered carried object 50 b mayperform other measurements, while the third sensing untethered carriedobject may not perform any measurement and be used as a plain untetheredobject. Such combination example could be useful for rationalizing thedifferent sensing untethered carried objects 50, and provide variouscombination for usage in a well. The combination of sensing untetheredcarried objects 50 may also be useful regarding a dissolving versusnon-dissolving of each sensing untethered carried object, wherebydissolution characteristics, such as dissolution rate or dissolutionproportion, may be different for each sensing untethered carried object50 a, 50 b or 50 c.

FIG. 21 represent an isometric view of the cup 51, within a cut viewportion of the plugging element 6 and inside a cut view of the tubingstring 8. The right portion of the FIG. 21 represents the same view asthe left portion of FIG. 21, with the addition of three sensinguntethered carried objects 50 a, 50 b and 50 c, which are landed on eachcup contact line 54 of each orifice 53. Again, a similar method andapparatus would be appropriate with another number of sensing untetheredcarried objects 50 and orifices 53, typically between one and ten.

FIG. 22 represent another isometric view of the right portion of FIG.21. Three sensing untethered carried objects 50 a, 50 b and 50 c areseated on the cup contact line 54 of each orifice 53, within the cup 51.The cup 51 being seated on the plugging element 6 at the contact zone52, and the plugging element 6 positioned within the tubing string 8.The combination of the sensing untethered carried objects 50 a, 50 b, 50c, the cup 51 and plugging element 6, would provide an isolation withinthe tubing string 8, from the uphole direction 23 towards the downholedirection 24, while also providing measurement possibilities towardsboth uphole and downhole direction 23 and 24, inside the well fluid 7 bythe different sensing untethered carried object 50 a, 50 b and 50 c.

FIG. 23 represents another embodiment of the invention.

FIG. 23 represents a similar view as FIG. 2. In the configuration ofFIG. 23, the toolstring 10 is in the position within the tubing string 8to position a subsequent plugging element 17 in its retracted form. Thedifference comes from a communication module 11, part of toolstring 10.The communication module 11 is either self-powered or powered throughthe wireline 15 connecting the toolstring 10 to surface 12. Thecommunication module 11 typically includes a receiving module and asending module to comminute data or commands to the untethered sensingobject 1 and communicate data or commands back to surface through thewireline 15 or after the toolstring 10 has been retrieved back tosurface 12.

FIG. 24 represents a close-up view of toolstring 10, at the positionwhere a subsequent plugging element 17, shown in its retractedconfiguration could be set inside the tubing string 8.

FIG. 25 represents a possible on-way or two-ways communication betweenthe sensing untethered object 1 and the communication module 11 of thetoolstring 10. Data communication could occur through the well fluid 7or through the tubing string 8 or a combination thereof [more info . . .] Communication through well fluid 7, symbolized by waves 25, couldoccur through acoustic, pressure, optical, electrical, magnetic orelectromagnetic wave. In particular, capacitive coupling can be realizedas an efficient way to communicate, with low energy requirements andrelatively high communication rates. Communication through tubing string8, symbolized as waves 26, could occur through acoustic, electrical,magnetic or electromagnetic. Similarly, a capacitive coupling can beachieved providing adequate contact with the casing. Depending on thepower required to send and receive signal between the untethered sensingobject 1 and the communication module 11, the distance between the two,a distance ranging from 0 foot [0 meter] to 3000 feet [1000 meters] maybe suitable for the described communication

A one-way communication from the untethered sensing object 1 towards thecommunication module 11, may include the recorded data from the varioussensing devices 4 present inside the untethered sensing object 1 andprocessed by the transmitter inside the electronic module 5 of theuntethered sensing object 1. Note that the amount of data transmitted inthis mode might be less than the over data recorded by the sensingdevices 4 of the untethered sensing object 1. For example, the timeframeor the frequency of data recording could be reduced, as a possibility toreduce the amount of transmitted data, typically if a transmissionlimitation existed while the untethered sensing object 1 andcommunication module 11 are inside the well fluid 7. Other options toretrieve the data will be represented in FIG. 31 to FIG. 34.

A two-way communication between the untethered sensing object 1 andcommunication module 11 could include, in addition to the one-waycommunication described previously, commands being sent from thecommunication module 11 to the untethered sensing object 1. Commandscould include modification of sensing or recording by the untetheredsensing object 1. For example, the communication module 11 could orderthe untethered sensing object to stop recording one or more parameters,to start recording other parameters, modifying the frequency of sensingor recording of the parameters. Command could also order a mechanicalaction, such as fluid entry port opening or closing in order to modifythe isolation status of the untethered sensing object 1, or in order tomodify the dissolving characteristics of the untethered sensing object1.

The transmitted data of the untethered sensing object 1 towards thecommunication module 11 could be stored inside the communication module11 and retrieved when the toolstring 10 is back at surface 12, asfurther described in FIG. 28.

The communication module 11 could also send the transmitted data tosurface 12 in a live fashion, through the wireline 15, and be retrievedinside a surface unit 16. Direct action on further operation could bedecided immediately such as modifying the position of the subsequentsetting of plugging element 6 or position of perforations defining theentry points of the fracturing channels 13.

FIG. 26 represents the possible setting of the plugging element 6 insidethe tubing string 8 while data transmission is happening from theuntethered sensing object 1 to the communication module 11.

FIG. 27 represents a subsequent step of FIG. 26 whereby the toolstring10 is retrieved after the plugging element 6 has been set inside thetubing string 8. Communication between the untethered sensing object 1and the communication module 11 could continue as long as distanceallows transmission.

FIG. 28 represents a subsequent step of FIG. 27 whereby the toolstring10 is back at surface. Further data retrieval could be done byconnecting the communication module 11 to another acquisition system. Anexample of surface data retrieval could be done with a USB connectionlinked to a surface computer.

Recording the data for each stage allows adapting the operationsparameters of the subsequent stages. Using data from the currentoperation along with data from relevant past wells, modified parametersfor the next stages can be automatically calculated by updating a modelin close real time. Such an automated response is often referred to asAI, or Artificial Intelligence.

In the example of FIG. 28, parameters of subsequent stage 14 e could beadapted based on past experience. Input parameters to be adapted includeposition of the plugging element 6 inside the tubbing string 8, positionof the entry points of the fracturing channels 13, pumping parameterslike fluid volume pumped, pressure ramping and level pumped, pumpingtime, proppant concentration and schedule, additional chemical insidestimulation fluid. The optimization could be based on final outputparameters like well production, rate, duration. The adjusting parameterwould the recorded data by the untethered sensing object 1 stage bystage.

Direct feedback and Artificial Intelligence from stage to stage would bepossible for different operation extent and magnitude. Typical extentwould be within a single well operation, a full pad, including zipperparallel operation, or full basin operation.

FIG. 29 represents another possible function of the untethered sensingobject 1.

In the represented embodiment of the untethered sensing object 1, somecomponents are dissolving while other components are not. Asrepresented, the external shell 2, also represented in two matchingsection 2 a and 2 b in FIG. 11, may be built out of dissolving material.The sensor protectors 22, possibly positioned in front of each sensingdevices 4 a, 4 b or 4 c, may also be built out of dissolvable material.The dissolvable material may be chosen, along with possible coatings, todissolve within a certain time frame from one hour to multiple weeks,depending on conditions of well fluid 7, such conditions include thechemical composition, the salinity, the pH, the temperature, the watercontent.

As described previously on FIG. 11, the untethered sensing object wouldprovide an isolation together with a plugging element 6, as dimension 61of the external shape of the untethered sensing object is greater thanthe dimension 60 of the internal shape of plugging element 6. On FIG.29, with the external shell 2 being dissolved, the new external shapedimension 62 of the core untethered sensing object 1 would now besmaller than dimension 60 of the internal shape of the plugging element6. Therefore, the core untethered sensing object 1 would not provide anymore isolation of well fluid 7 with the plugging element 6, and would beable to pass through uphole 23 or downhole 24.

Note that the core sensing function of the untethered sensing objectcould still be operational, even without the shell 2, being partially orfully dissolved.

FIG. 30 represents a larger view of wellbore section with two sectionsas represented in FIG. 29. FIG. 30 depicts the position of two pluggingelements 6 and two cores of untethered sensing objects 1, having a freemovement inside the well fluid 7 of the tubing string 8. The arrow 70represents the potential movement of the core untethered sensing object1 upwards of the plugging element 6 associated with the untetheredsensing object 1. The arrow 71 represents the potential movement of thecore untethered sensing object 1 downwards of the plugging element 6associated with the untethered sensing object 1. Movement 70, in theuphole direction within the tubing string, could come from a flowbackinside the well, induced by well production from the formationreservoir, including potential well lifting, with help of pumping.Movement 71, in the downhole direction within the tubing string, couldcome from a pumping inside the well, induced by surface pumping or sidetubing injection pumping.

FIG. 31 represents a wellbore cross-section view with five stagescompleted 14 a, 14 b, 14 c, 14 d, and 14 e. A flowback with upwardsmovement 70, allows the core of untethered sensing object 1 to flow backthrough the multiple set plugging elements 6. Depending on dissolvingrates of the shell of the untethered sensing object 1 and the pluggingelement 1, this flowback and pass-through of the core of untetheredsensing object may happen between one hour and one year after thecompletion of the last stage, depicted here as 14 e.

Note that the flowback and potential retrieval of the core of theuntethered sensing object 1 can have some advantages, which will beexposed along FIG. 33. It may also be possible as a well completionsoperation to have the whole untethered sensing object dissolve or belimited to small parts of non-dissolving sections, which would stayinside the wellbore and never be retrieved.

FIG. 32 represents a wellbore cross-section, and is a subsequent step ofFIG. 31. The four cores of the untethered sensing object 1 are now closeto surface 12, inside the vertical section of the tubing string 8. Asufficient flow back flowrate 72 of well fluid 7 would be necessary tocarry the cores of untethered sensing object 1 back to surface. Theflow-back flowrate 72 could occur through natural flow from thereservoir, as over-pressure, or necessitate a pumping action, fromsurface or downhole, as submersible pumps, or necessitate an injectionaction from a side well or side injection points on the tubing string.

If flow-back rate is not sufficient, or for other operating reasons,other ways of retrieving the cores of untethered sensing object 1 backto surface would be possible. A possibility would be to bring downinside the tubing string 8 another toolstring, whether on wireline, oncoiled tubing, on slickline or tractor, and having a mechanicalretrieval section on the toolstring able to catch one or more cores ofuntethered sensing object 1 during each trip. A retrieval section on atoolstring could have the shape of a ball catcher with ratchetingsection within a tubular member. Another example of retrieval action ona toolstring could be magnetic whereby a portion of the core of theuntethered sensing object include a magnetic material.

FIG. 33 is a close-up view of the cross-section of FIG. 32. FIG. 33represents the detail of one core of untethered sensing object 1 beingretrieved to surface 12, passing the tubing connections upstream of thetubing string 8. Typically, a part catcher will be present at surface tocollect one or more cores of untethered sensing object 1, often known asball catcher and used to catch non-dissolving objects like phenolicballs in other types of operations.

Having the cores of untethered sensing object 1 back at surface mayprovide two key advantages. First would be to enable additional dataretrieval. In addition to the data transmitted to the communicationmodule 11 of the toolstring 10 as depicted in FIG. 25, additional datamay have been recorded afterwards by the untethered sensing object 1,like data regarding subsequent stages stimulated afterwards. Also, theamount of data may be greater, if for example only a limited time anddata transmission rate was available for the transmission with thecommunication module 11 of the toolstring 10, only a portion of the datamay have been retrieved downhole. At surface, the entire data log of allsensing devices could be retrieved and transmitted through auser-friendly plug-and-play system. For example, the core of theuntethered sensing object 1 may include a connector, like a USB allowingto wire connect to an interpretation unit at surface. As anotherexample, the core of the untethered sensing object 1 may include awireless module able to communicate with radio frequencies, likeBluetooth, to a surface unit.

A second advantage would be the possible re-use of the core ofuntethered sensing object 1, after data retrieval, maintenance, resetand repower. A potential new shell 2 and new sensor protectors 22 may bere-assembled around the retrieved core to create a new untetheredsensing object 1, which can be used multiple times for additionaloperations.

FIG. 34 represents a wellbore cross-section, as a subsequent step ofFIG. 32. In FIG. 34, all cores of untethered sensing objects (1) havebeen retrieved, and the tubing string 8 is left with plugging members 6.

FIG. 35 represents a wellbore cross-section, as a subsequent step ofFIG. 34. In FIG. 35 the plugging members 6, built out of dissolvablematerial, have fully dissolved, or left small non-dissolvable particles,such as screws or buttons, which do not restrict the flow withing thetubing string 8.

Note that the sequence of dissolving could be defined by differentdissolvable material choices or design constraints such as thickness andsurface amount of well fluid 7 contact. For ease of understanding, fromFIG. 29 to FIG. 35, the dissolving sequence is first the shell 2 of thesensing untethered object 1 and then the plugging element 6, though bothcomponent dissolving may occur simultaneously and allow a similarretrieval sequence for the core of the sensing untethered object 1.

FIG. 36 represents another embodiment for the untethered sensing object1. This embodiment could be referred to as a pill. FIG. 36 represents anisometric cut view of the pill untethered sensing object 1.

The descriptions made in FIG. 10 for a spherical untethered sensingobject 1 may still be valid. This is the case for the electronics module5, the wiring 21, the sensing carrier 19, the sealing section 20, thesensing devices 4 a and 4 b, the sensor protector 22, and orificechannel 3. The main visible difference comes from the external shape ofthe shell sections 2 a and 2 b. The shell sections 2 a and 2 b aredisplayed as a combination of cylindrical and spherical sections, thecross-section may be referred to as a stadium shape or obround.

As referred in FIG. 10, other shapes for the shell sections 2 arepossible. Close to the depicted shape in FIG. 36 could be across-section in the shape of an ellipse, an oval, a polygon.

One advantage of a pill shape would be the possibility to have a longaxis, represented along the two sensing devices 4 a and 4 b and a shortaxis, passing about the junction 25 between the two shell sections 2 aand 2 b. The two-axis shape may help to orient the untethered sensingobject 1 within a tubing string as depicted in FIG. 39.

FIG. 37 is another view of the same pill untethered sensing object 1,described in FIG. 36, as a cross-section view.

FIG. 38 is another view of the same pill untethered sensing object 1,described in FIG. 36, as an external isometric view.

FIG. 39 represents a cross-section view of a tubing string 8 sectionincluding a plugging element 6 and a pill untethered sensing object 1.FIG. 39 may be comparable with FIG. 11 depicting a spherical untetheredsensing object 1 on a plugging element 6.

The long axis of the pill untethered sensing object 1, represented asdimension 63, may be greater than the internal diameter of the tubingstring 8, represented as dimension 64. Therefore, the pill untetheredsensing object 1 may have a constrained orientation within the tubingstring, and when landing on the plugging element 6, be constrained tohave its long axis nearly aligned with a theoretical axis of the tubingstring 8. The alignment angle would typically be between 0 and 30degrees.

The short axis of the pill untethered sensing object 1, represented asdimension 61, may be greater than the internal dimension of the pluggingelement, typically diameter of a circular shape, represented asdimension 60. Therefore, the pill untethered sensing object 1 may bestopped on the plugging element 6, at the contact line 30, and providewell fluid isolation. The pill untethered sensing object 1 may alsowithstand differential pressure of well fluid 7 across its volume fromuphole 23 to downhole 24.

A potential advantage of this pill configuration in regards to itsposition on a plugging element 6 would be the possibility to predict theorientation of the different sensing devices 4. This advantage would forexample not be present with a sphere shape, since a sphere shape cannotbe oriented geometrically within annulus elements, such a tubing string8, and typically a plugging element 6. Predicting the position of thedifferent sensing devices could simplify the data recording for uphole23 and downhole 24 measurements. It would also allow to limit the numberof sensing devices, down to two, in case both uphole 23 and downhole 24measurements are necessary across the contact line 30. For a sphereshape of untethered sensing object as depicted in FIG. 15, four sensingdevices position would typically be necessary to ensure uphole 23 anddownhole 24 measurement across contact line 30.

The pill untethered sensing object 1 may have the same materialcharacteristic options as the sphere untethered sensing object 1described in FIG. 10. Namely, some part or the whole of the pilluntethered sensing object 1 may include dissolvable materials. Forexample, the shell sections 2 as well as sensor protector 23 could bebuilt out of dissolvable material so that the pill untethered sensingobject 1 has similar characteristics as described in FIG. 29. A core ofpill untethered sensing object may remain, having cross-sectionaldimension 62. The dimension 62 may be smaller than the plugging elementinternal dimension 60, and therefore allow similar functions asdescribed in FIGS. 29 to 33, for the core of the pill untethered sensingobject 1.

FIG. 40 represents a cross-section view of a wellbore with a pilluntethered sensing object 1, landed on a plugging element 6 of stage 14d.

What is claimed is:
 1. A method comprising: placing an untetheredsensing object inside a well fluid of a wellbore, whereby the untetheredsensing object can perform sensing, data recording and data transmittingof well fluid and wellbore parameters; sensing and data recording ofwell fluid and wellbore parameters by the untethered sensing objectwhile being in the well fluid; conveying from surface a toolstringincluding a communication module, inside the well fluid of the wellbore,after the untethered sensing object has been placed inside the wellfluid of the wellbore, wherein the toolstring reaches a proximitydistance between 0 ft and 3,000 ft [0 m and 1000 m] from the untetheredsensing object; transmitting recorded data by the untethered sensingobject towards the communication module of the toolstring, after thetoolstring has been conveyed from surface inside the well fluid of thewellbore; retrieving at surface transmitted recorded data from thecommunication module of the toolstring.
 2. The method of claim 1,wherein the toolstring is conveyed via wireline, coiled-tubing,slickline, pipe or tractor.
 3. The method of claim 1, wherein thewellbore comprises tubing, cemented or non-cemented casing or open-hole.4. The method of claim 1, wherein sensing and data recording of wellfluid and wellbore parameters comprises the sensing and data recordingof fluid pressure, fluid temperature, fluid flow, fluid properties likecomposition, density, resistivity, salinity, pH, wellbore propertieslike casing collar locator, casing thickness, cement bound, formationproperties like formation acoustic, resistivity, porosity, permeability,natural radioactivity.
 5. The method of claim 1, wherein retrieving atsurface transmitted recorded data occurs while the communication moduleof the toolstring is either downhole inside the well fluid or on theground back at surface.
 6. The method of claim 1, wherein transmittingrecorded data of the untethered sensing object towards the communicationmodule of the tool string includes wireless transmission, bluetoothtransmission, acoustic transmission, electromagnetic transmission,electric transmission, capacitive coupling, either through the wellfluid, or the wellbore, or through physical contact of the communicationmodule of the toolstring with the untethered sensing object.
 7. Themethod of claim 1, wherein placing an untethered sensing object inside awell fluid of a wellbore, includes launching the untethered sensingobject from surface or releasing it from the toolstring inside thewellbore.
 8. The method of claim 1, wherein sensing and data recordingof well fluid and wellbore parameters by the untethered sensing objectincludes sensing and data recording during one or more stimulationpumping stages, wherein the duration of a stimulation pumping stage isbetween 0.1 and 24 hours, and the number of stimulation pumping stageswithin one wellbore is between 1 and 100; wherein a stimulation pumpingstage includes pumping a stimulation fluid from surface towards awellbore portion comprising fluid entry points to the ground formationsurrounding the wellbore, and isolated from additional wellbore portionsdownhole or below a plugging element; wherein the untethered sensingobject is in contact with the plugging element or within a distance of100 feet [30 m] uphole or above the plugging element; wherein theplugging element is a fracturing plug, a bridge plug, a seat, a sleeveseat or a packer.
 9. The method of claim 8, wherein transmitting ofrecorded data from the untethered sensing object to the communicationmodule of the toolstring occurs during the setting of the pluggingelement of a subsequent uphole stimulation pumping stage, whereby thesetting of the plugging element is performed by the toolstring insidethe wellbore.
 10. The method of claim 8, further comprising adjustingspecifications of subsequent stimulation pumping stages, after theretrieval at surface of transmitted recorded data; whereinspecifications adjustment of subsequent stimulation pumping stagesincludes the adjustment of plugging element placement, fluid entrypoints placement, stimulation fluid parameters comprising pumping rate,pressure and duration, stimulation fluid variables comprising addedchemicals type and concentration, viscosity, proppant selection andconcentration, fiber selection and concentration.
 11. The method ofclaim 8, wherein the untethered sensing object include a materialdissolvable by well fluid.
 12. The method of claim 11, furthercomprising dissolving the outer shape of the untethered sensing objectto a remaining non-dissolved core untethered sensing object, whereby thecore untethered sensing object is able to pass across one or multipleplugging elements; retrieving the core untethered sensing object back tosurface, through floating, flowback or toolstring conveyance; collectingrecorded data by the untethered sensing object at surface, from the coreuntethered sensing object, wherein the collected recorded data from theuntethered object is cumulative from the recorded data previouslytransmitted to the communication module of the toolstring inside thewell fluid of the wellbore.
 13. An apparatus, for use inside a wellfluid of a wellbore, comprising: a toolstring including: a communicationmodule; an untethered sensing object including: at least one sensor anacquisition module a data recording module a data transmitting modulewherein the at least one sensor measures well fluid and wellboreparameters and converts the measurement into an electrical signal;wherein the acquisition module collects the electrical signal from theat least one sensor and converts the electrical signal in a form ofnumerical data, whereby the electrical signal collection occurs througha wired or wireless connection; wherein the data recording module storesthe numerical data inside a memory; wherein the data transmitting moduletransmits the recorded data to the communication module of thetoolstring, when the toolstring is at a distance between 0 foot to 3,000feet [0 m to 1,000 m] from the untethered sensing object, inside thewell fluid of the wellbore; wherein the communication module of thetoolstring retrieves the transmitted data from the untethered sensingobject; wherein the communication module sends the retrieved transmitteddata to the surface via an electrical connection linked with thetoolstring conveyance way within the wellbore, wherein the toolstringconveyance way includes wireline, coiled tubing, slickline, drill pipe.14. The apparatus of claim 13, wherein the untethered sensing object isa ball, a dart, a pill.
 15. The apparatus of claim 13, wherein theuntethered sensing object comprises material dissolving inside wellfluid.
 16. The apparatus of claim 15, wherein the untethered sensingobject includes an external shell surrounding a core of the untetheredsensing object, wherein the core includes at least the data recordingmodule and the data transmitting module.
 17. The apparatus of claim 16,wherein the external shell includes dissolvable material and wherein thecore is non-dissolvable and has a density lower than the density of thewell fluid.
 18. The apparatus of claim 13, wherein the communicationmodule of the toolstring includes a 2-way transmission possibility withthe untethered sensing object, allowing to send commands to theuntethered sensing object, in addition to receiving transmitted datafrom the untethered sensing object.
 19. The apparatus of claim 13,wherein the data transmitting module of the untethered sensing objectincludes a read-out port to retrieve the recorded data, whereas theuntethered sensing object is outside of the well fluid of the wellbore.20. The apparatus of claim 13, wherein the communication module of thetoolstring includes a read-out port to retrieve additional transmitteddata from the untethered sensing object, whereas the communicationmodule of the toolstring is outside of the well fluid of the wellbore.